The Intergovernmental Panel on Climate Change (IPCC) “took a hit” when it released its Fourth Assessment Report in 2007. That Report contained one significant error (the claim that Himalayan glaciers would disappear by 2035). Soon after the report was issued, the “Climategate” controversy broke out. Critics suggested that factual statements in the report had been edited to support a global warming theory.
Although independent peer reviews confirmed these “edits” were appropriate, the tag “Climategate” stuck. Denialists attacked subsequent IPCC analysis of climate change issues by linking the analysis to alleged deliberate misrepresentations in the Fourth Report. To Denialists, Climategate was proof of a underlying unscientific bias that undermined any IPCC conclusions.
If one can judge by the commentary on the draft text of the soon-to-be- released Fifth Assessment Report, the IPCC has attempted to avoid controversy over this report. The language in the report is temperate even if the global warming crisis isn’t.
In this soon-to-be-released Report the IPCC will claim “as a virtual certainty” that human activity – the burning of fossil fuels – is the cause of global warming. The use of the term virtual is consistent with the empirical nature of the evidence on which the Fifth Report relies. Yet the public will not appreciate the reason for the qualification implicit in that word. The use of such language will create doubt, a legacy of Climategate.
The Denialists will attack the Report on a new ground. Over the last seventeen years, the level of CO2 has been steadily increasing by relatively small yearly increments. At the same time the world average temperatures have remained basically constant. So the Denialists will claim CO2 can’t be the cause, as there would have been a rise in temperature consistent with the increased level of this greenhouse gas.
The Fifth Report will express “medium confidence” that the slowing of the rise in temperature is “due in roughly equal measure” to natural variations in the weather and to other factors affecting energy reaching the Earth’s surface. These factors could include:
- greater-than-expected quantities of ash from volcanoes (the Iceland eruption that played havoc with Atlantic international air schedules),
- a decline in heat from the sun during a current 11-year solar cycle;
- more heat being absorbed by the deep oceans;
- or the possibility that the climate may be less sensitive than expected to a build-up of carbon dioxide.
Or maybe the latest decade is just a blip!
The Fifth Report will resolve some but regrettably not all public doubts over climate change. Environmental organizations will have to take up the challenge of explaining this Report to John and Jane Q. Public.